Develop Reference

Why do I need to explicitly call app.listen(port) in order to make express-ws working?

I'm new to NodeJS Express, I was following the official tutorial from express-ws to setup websocket in the simple project generated by npx express-generator . In the app.js, I've to explicitly call the app.listen(3000) in order to make the ws connection working. Am I doing this correctly although it is working ? What's the difference between app.listen vs. server.listen in this case? what is app.set(port,port) in www.js used for?
app.js - I've to add the last line below:
var createError = require('http-errors');
var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var logger = require('morgan');
var app = express();
var expressWs = require('express-ws')(app);
var indexRouter = require('./routes/index');
var usersRouter = require('./routes/users');
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
app.use('/', indexRouter);
app.use('/users', usersRouter);
// catch 404 and forward to error handler
app.use(function(req, res, next) {
next(createError(404));
});
// error handler
app.use(function(err, req, res, next) {
// set locals, only providing error in development
res.locals.message = err.message;
res.locals.error = req.app.get('env') === 'development' ? err : {};
// render the error page
res.status(err.status || 500);
res.render('error');
});
module.exports = app;
app.listen(3001)// for websocket listen port
www.js - this file was generated by the express-generator and I see it's already calling app.set('port',port) and server.listen(port)
#!/usr/bin/env node
/**
* Module dependencies.
*/
var app = require('../app');
var debug = require('debug')('xapp:server');
var http = require('http');
/**
* Get port from environment and store in Express.
*/
var port = normalizePort(process.env.PORT || '3000');
app.set('port', port);
/**
* Create HTTP server.
*/
var server = http.createServer(app);
/**
* Listen on provided port, on all network interfaces.
*/
server.listen(port);
server.on('error', onError);
server.on('listening', onListening);
/**
* Normalize a port into a number, string, or false.
*/
function normalizePort(val) {
var port = parseInt(val, 10);
if (isNaN(port)) {
// named pipe
return val;
}
if (port >= 0) {
// port number
return port;
}
return false;
}
/**
* Event listener for HTTP server "error" event.
*/
function onError(error) {
if (error.syscall !== 'listen') {
throw error;
}
var bind = typeof port === 'string'
? 'Pipe ' + port
: 'Port ' + port;
// handle specific listen errors with friendly messages
switch (error.code) {
case 'EACCES':
console.error(bind + ' requires elevated privileges');
process.exit(1);
break;
case 'EADDRINUSE':
console.error(bind + ' is already in use');
process.exit(1);
break;
default:
throw error;
}
}
/**
* Event listener for HTTP server "listening" event.
*/
function onListening() {
var addr = server.address();
var bind = typeof addr === 'string'
? 'pipe ' + addr
: 'port ' + addr.port;
debug('Listening on ' + bind);
}

The .listen(port) method on either a server object or on the Express app object is what actually starts your server so that it is listening for incoming requests. Without that, you don't have a running http server. And, you need a running http server for both Express and for your webSocket. If you don't call something that triggers server.listen(), then you won't have a running server. It will be all configured and waiting to start, but won't yet be running.
If you look at the code for app.listen(), it is just a helper function. All, it does is this:
app.listen = function listen() {
var server = http.createServer(this);
return server.listen.apply(server, arguments);
};
It creates an http server object and then calls .listen() on it. It's just a shortcut. If you have a reason to want to create your own http server object and then call server.listen() on that one, you can do it that way too. In fact, if you're starting an https server, you have to do it that way because you have to pass the right arguments to https.createServer() which app.listen() doesn't do for you.

How to setup clusters in expressjs 4.x app?

I have an expressjs generated app which is configured with socket io and I would like to implement nodejs clusters in it. The problem is that in Express 4.x the server listening configuration is in the bin/www file and no longer in app.js file.
Also my app is configured with socket io so I don't want to brake it too.
This is how it should be implemented in express apps according to this article:
app.js
// Include the cluster module
var cluster = require('cluster');
// Code to run if we're in the master process
if (cluster.isMaster) {
// Count the machine's CPUs
var cpuCount = require('os').cpus().length;
// Create a worker for each CPU
for (var i = 0; i < cpuCount; i += 1) {
cluster.fork();
}
// Listen for dying workers
cluster.on('exit', function (worker) {
// Replace the dead worker, we're not sentimental
console.log('Worker %d died :(', worker.id);
cluster.fork();
});
// Code to run if we're in a worker process
} else {
// Include Express
var express = require('express');
// Create a new Express application
var app = express();
// Add a basic route – index page
app.get('/', function (request, response) {
console.log('Request to worker %d', cluster.worker.id);
response.send('Hello from Worker ' + cluster.worker.id);
});
// Bind to a port
app.listen(3000);
console.log('Worker %d running!', cluster.worker.id);
}
And this is what I have:
app.js
var createError = require('http-errors');
var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var logger = require('morgan');
var indexRouter = require('./routes/index');
var app = express();
var io = app.io = require('socket.io')();
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'pug');
app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
app.use('/', indexRouter);
// catch 404 and forward to error handler
app.use(function(req, res, next) {
next(createError(404));
});
// error handler
app.use(function(err, req, res, next) {
// set locals, only providing error in development
res.locals.message = err.message;
res.locals.error = req.app.get('env') === 'development' ? err : {};
// render the error page
res.status(err.status || 500);
res.render('error');
});
var players = {};
//socket io
io.on('connection', function(socket) {
socket.on('new player', function(data) {
var player = {
id: socket.id,
name: data.name,
color: data.color
}
players[socket.id] = player;
io.to(`${socket.id}`).emit('player info', player);
});
socket.on('chat', function(data) {
io.emit('message', {
player: players[data.id],
text: data.text
});
});
socket.on('disconnect', function() {
delete players[socket.id];
});
});
module.exports = app;
bin/www
#!/usr/bin/env node
/**
* Module dependencies.
*/
var app = require('../app');
var debug = require('debug')('elvin:server');
var http = require('http');
/**
* Get port from environment and store in Express.
*/
var port = normalizePort(process.env.PORT || '80');
app.set('port', port);
/**
* Create HTTP server.
*/
var server = http.createServer(app);
var io = app.io
io.attach(server);
/**
* Listen on provided port, on all network interfaces.
*/
server.listen(port, function(){
console.log('server listening on port ' + server.address().port);
});
server.on('error', onError);
server.on('listening', onListening);
/**
* Normalize a port into a number, string, or false.
*/
function normalizePort(val) {
var port = parseInt(val, 10);
if (isNaN(port)) {
// named pipe
return val;
}
if (port >= 0) {
// port number
return port;
}
return false;
}
/**
* Event listener for HTTP server "error" event.
*/
function onError(error) {
if (error.syscall !== 'listen') {
throw error;
}
var bind = typeof port === 'string'
? 'Pipe ' + port
: 'Port ' + port;
// handle specific listen errors with friendly messages
switch (error.code) {
case 'EACCES':
console.error(bind + ' requires elevated privileges');
process.exit(1);
break;
case 'EADDRINUSE':
console.error(bind + ' is already in use');
process.exit(1);
break;
default:
throw error;
}
}
/**
* Event listener for HTTP server "listening" event.
*/
function onListening() {
var addr = server.address();
var bind = typeof addr === 'string'
? 'pipe ' + addr
: 'port ' + addr.port;
debug('Listening on ' + bind);
}
What do I do? The module.exports = app; is what it is causing me troubles

I use my own boiler plate. I used socket, cluster and express together in it. Here is a link to it.
Desktop-CHAT-app
You can download it and make the changes over here and proceed. I've used many useful packages too.
Hope it helps!

Error setting up simple server with middleware on node.js express

I am reasonably new to node express and am trying to set up a simple server with middleware to handle routing.
The error I'm getting is TypeError: Router.use() requires a middleware function but got a Object
The error is because of the app.get('/', require(routes)); line. Does anyone know what I need to put here as a middleware function?
//server.js
http = require('http');
let port = process.env.PORT || 3000;
let host = '127.0.0.1';
var express = require('express');
var app = express();
var routes = './api/routes/positions';
app.use('/', require(routes));
http.createServer(app).listen(port);
console.log('Listening at http://' + host + ':' + port);
//#########################
//positions.js
const express = require('express');
var router = express.Router();
router.get('/', (err, req, res, next) => {
res.status(200).json({
message: "hello from server"
});
});
module.exports.router;

You are exporting the module in wrong way from positions.js file.
you need to write
module.exports = router
instead of,
module.exports.router
What you have written will bind a new key router to exports object, but haven't assigned any value to it and hence it goes back to default the empty object {}.
Now express was expecting a function but got object and hence the error. You can verify it by checking the require(routes) in server.js file.
Update (advice)
Please study this formatted version of your code.
const http = require('http');
const express = require('express');
const routes = require('./api/routes/positions');
const port = process.env.PORT || 3000;
const host = '127.0.0.1';
const app = express();
app.use('/', routes);
http.createServer(app).listen(port);
console.log('Listening at http://' + host + ':' + port);
If you want to read more project, you can read this boilerplate written by me. It's bit old, but may serve you well.

#!/usr/bin/env node
/**
* Module dependencies.
*/
var app = require('../app');
var debug = require('debug')('ag:server');
var http = require('http');
/**
* Get port from environment and store in Express.
*/
var port = normalizePort(process.env.PORT || '3002');
app.set('port', port);
/**
* Create HTTP server.
*/
var server = http.createServer(app);
/**
* Listen on provided port, on all network interfaces.
*/
server.listen(port);
server.on('error', onError);
server.on('listening', onListening);
/**
* Normalize a port into a number, string, or false.
*/
function normalizePort(val) {
var port = parseInt(val, 10);
if (isNaN(port)) {
// named pipe
return val;
}
if (port >= 0) {
// port number
return port;
}
return false;
}
/**
* Event listener for HTTP server "error" event.
*/
function onError(error) {
if (error.syscall !== 'listen') {
throw error;
}
var bind = typeof port === 'string'
? 'Pipe ' + port
: 'Port ' + port;
// handle specific listen errors with friendly messages
switch (error.code) {
case 'EACCES':
console.error(bind + ' requires elevated privileges');
process.exit(1);
break;
case 'EADDRINUSE':
console.error(bind + ' is already in use');
process.exit(1);
break;
default:
throw error;
}
}
/**
* Event listener for HTTP server "listening" event.
*/
function onListening() {
var addr = server.address();
var bind = typeof addr === 'string'
? 'pipe ' + addr
: 'port ' + addr.port;
debug('Listening on ' + bind);
}

Try this one:
//server.js
let port = process.env.PORT || 3000;
let host = '127.0.0.1';
var express = require('express');
var app = express();
var routes = require('./api/routes/positions');
http.createServer(app).listen(port);
console.log('Listening at http://' + host + ':' + port);
//#########################
//positions.js
const express = require('express');
var router = express.Router();
router.use('/', routes);
app.use('/', routes);
router.get('/', (err, req, res, next) => {
res.status(200).json({
message: "hello from server"
});
});
module.exports = router;

Why is socket.io giving me a 404 error?

I am basically trying to recreate a simple chat application posted on the official website of socket.io.
I created the following module in content.js:
var app = require('express');
var router = app.Router();
module.exports = function(app, io) {
app.get('/profile',function(req, res){
res.render('profile.ejs');
});
io.on('connection', function(socket){
socket.on('chat message', function(msg){
io.emit('chat message', msg);
});
});
return router;
};
I am calling it from index.js through this:
// socket.io
var server = require('http').Server(app);
var io = require('socket.io')(server);
require('./app/content')(app, io);
while running the app, nothing is being sent and the following error(s) are displayed in my console:
GET /socket.io/?EIO=3&transport=polling&t=1461512892706-14 404 2.370 ms - 1097
How can I fix this? as far as i read it got something to do with the location of profile.ejs? Thank you as always for any help
Here is index.js:
var express = require('express')
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var passport = require('passport');
var flash = require('connect-flash');
var session = require('express-session');
var routes = require('./routes/index');
var morgan = require('morgan');
var users = require('./routes/users');
var home = require('./routes/home');
var mysql = require('mysql');
var helmet = require('helmet');
var app = express();
// socket.io
var server = require('http').Server(app);
var io = require('socket.io')(server);
require('./config/passport')(passport); // pass passport for configuration
app.use(morgan('dev')); // log every request to the console
app.use(cookieParser()); // read cookies (needed for auth)
app.use(bodyParser.urlencoded({
extended: true
}));
app.use(bodyParser.json());
var connection = mysql.createConnection({
host: 'localhost',
user: 'root',
password: 'mysql',
database: 'clearreview'
});
connection.connect();
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');
// uncomment after placing your favicon in /public
//app.use(favicon(path.join(__dirname, 'public', 'favicon.ico')));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: false}));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
// security measure against xss attacks
app.use(helmet.xssFilter());
// hide powered by express
app.use(helmet.hidePoweredBy());
// security measure against sniffing
app.use(helmet.noSniff());
app.use('/', routes);
// required for passport
app.use(session({
secret: 'vidyapathaisalwaysrunning',
resave: true,
saveUninitialized: true
})); // session secret
app.use(passport.initialize());
app.use(passport.session()); // persistent login sessions
app.use(flash()); // use connect-flash for flash messages stored in session
// routes ======================================================================
//require('./app/cr-auth-routes.js')(app, passport); // load our routes and pass in our app and fully configured passport
require('./app/cr-auth-routes')(app, passport);
require('./app/search.js')(app, connection);
require('./app/content')(app, io);
// catch 404 and forward to error handler
app.use(function (req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
// error handlers
// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
app.use(function (err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: err
});
});
}
// production error handler
// no stacktraces leaked to user
app.use(function (err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: {}
});
});
module.exports = app;
www file that launches the server:
#!/usr/bin/env node
/**
* Module dependencies.
*/
var app = require('../app');
var debug = require('debug')('clear-review:server');
var http = require('http');
/**
* Get port from environment and store in Express.
*/
var port = normalizePort(process.env.PORT || '3000');
app.set('port', port);
/**
* Create HTTP server.
*/
var server = http.createServer(app);
/**
* Listen on provided port, on all network interfaces.
*/
server.listen(port);
server.on('error', onError);
server.on('listening', onListening);
/**
* Normalize a port into a number, string, or false.
*/
function normalizePort(val) {
var port = parseInt(val, 10);
if (isNaN(port)) {
// named pipe
return val;
}
if (port >= 0) {
// port number
return port;
}
return false;
}
/**
* Event listener for HTTP server "error" event.
*/
function onError(error) {
if (error.syscall !== 'listen') {
throw error;
}
var bind = typeof port === 'string'
? 'Pipe ' + port
: 'Port ' + port;
// handle specific listen errors with friendly messages
switch (error.code) {
case 'EACCES':
console.error(bind + ' requires elevated privileges');
process.exit(1);
break;
case 'EADDRINUSE':
console.error(bind + ' is already in use');
process.exit(1);
break;
default:
throw error;
}
}
/**
* Event listener for HTTP server "listening" event.
*/
function onListening() {
var addr = server.address();
var bind = typeof addr === 'string'
? 'pipe ' + addr
: 'port ' + addr.port;
debug('Listening on ' + bind);
}

It appears that you are creating two separate servers, one in your www file with:
var server = http.createServer(app);
And, another one in index.js with:
var server = require('http').Server(app);
You are never starting the one created in index.js and that's the one that socket.io is connected to so that's why you don't have any socket.io functionality. The server you bound socket.io to was never started.
You are starting the one your www file, but it has no socket.io connected to it.
You need to create one server and only one server and have that be the server that Express and socket.io are bound to. And, then you need to start that one server.

app.set('port', port) 'TypeError: undefined is not a function'. Beginner, need ideas

I'm an amateur learning to build with node.js. I've been following a tutorial to create my first node.js app. It worked perfectly until I entered 'npm start'. The log is:
C:\node\nodeteest3\bin\www:16
TypeError: undefined is not a function
at Object.<anonymous> M+<C;\node\nodetest3\bin\www:16:5
at Module_compile (module.js:460:26)
at Object.Module._extensions..js (module.js:478:10)
at Module.load (module.js:355:32)
at Function.Module._load (module.js:310:12)
at Function.module.runMain (module.js:501:10)
at startup(node.js:129:16)
at node.js:814:3
Then it output about 20 lines starting with "npm ERR! " + filepaths, that I don't think are necessary, as the error seems to be in the bin file. The code for this is
#!/usr/bin/env node
/**
* Module dependencies.
*/
var app = require('../app');
var debug = require('debug')('nodetest3:server');
var http = require('http');
/**
* Get port from environment and store in Express.
*/
var port = normalizePort(process.env.PORT || '3000');
This is where the error points to:
[app.set('port', port);]
-------^error pointer at 's'-so clearly about set------------
app.set('port', port);
/**
* Create HTTP server.
*/
var server = http.createServer(app);
/**
* Listen on provided port, on all network interfaces.
*/
server.listen(port);
server.on('error', onError);
server.on('listening', onListening);
/**
* Normalize a port into a number, string, or false.
*/
function normalizePort(val) {
var port = parseInt(val, 10);
if (isNaN(port)) {
// named pipe
return val;
}
if (port >= 0) {
// port number
return port;
}
return false;
}
/**
* Event listener for HTTP server "error" event.
*/
function onError(error) {
if (error.syscall !== 'listen') {
throw error;
}
var bind = typeof port === 'string'
? 'Pipe ' + port
: 'Port ' + port;
// handle specific listen errors with friendly messages
switch (error.code) {
case 'EACCES':
console.error(bind + ' requires elevated privileges');
process.exit(1);
break;
case 'EADDRINUSE':
console.error(bind + ' is already in use');
process.exit(1);
break;
default:
throw error;
}
}
/**
* Event listener for HTTP server "listening" event.
*/
function onListening() {
var addr = server.address();
var bind = typeof addr === 'string'
? 'pipe ' + addr
: 'port ' + addr.port;
debug('Listening on ' + bind);
}
Like I said in the beginning, I'm a complete beginner with command-line/github, but I'm already in love with it. I try to practice it every night after I finish my homework, and am getting really frustrated about getting stuck because I haven't been able to move forward for four days now. Also, I'm running this on node.js and the OS is Windows 8. Anything helps! Let me know if you want me to post any of the other code; I omitted so as to not add more than necessary.
"../app (app.js file) JUST ADDED"***************************
../app file:
[ App.js ]
var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var routes = require('./routes/index');
var users = require('./routes/users');
var app = express();
/// catch 404 and forwarding to error handler
app.use(function(req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
var app = express();
// error handlers
// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
app.use(function(err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: err
});
});
}
var app = express();
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
// uncomment after placing your favicon in /public
//app.use(favicon(__dirname + '/public/favicon.ico'));
app.use(logger('dev'));
app.use(bodyParser.json({estended: true}));
app.use(bodyParser.urlencoded({extended: true}));
app.use(cookieParser({extended:true}));
app.use(express.static(path.join(__dirname, 'public')));
app.use('/', routes);
app.use('/users', users);
// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: {}
});
});

You are not exporting anything in the app.js file. At the end of app.js file, include following line.
module.exports = app;
See whether your problem goes away.
And one more addition: you have var app = express(); twice in your app.js.

You don't have declared any function called set inside the app.js file.
Create that function and export it like this:
exports.set = function(...) { ... };
If this app is the express app yo especify a port like this:
var express = require('express'),
http = require('http');
var app = express();
http.createServer(app).listen(port);
instead of
app.set('port', port);
/**
* Create HTTP server.
*/
var server = http.createServer(app);
This is because the port is a property of the http server and not of the express app
You can use also
var express = require('express'),
app = express();
app.listen(port);

Intaned of calling export please use module.export end the end of your script.
exports = app;
module.exports = app;

At the bottom of your app.js:
app.set('port', process.env.PORT || 26398); //<--- replace with your port number
// Server
var server = http.createServer(app);
server.listen(app.get('port'), function(){
console.log('Express server listening on port ' + app.get('port'));
});
module.exports = app;

In my case I simply moved the normalizePort function before the function was called. This was in coffeescript but I've converted it to javascript here.
normalizePort = function(val) {
var port;
var port;
port = parseInt(val, 10);
if (isNaN(port)) {
return val;
}
if (port >= 0) {
return port;
}
return false;
};
port = normalizePort(process.env.PORT || '4000');

Just add "module.exports=app;" in the app.js file.